CVE-2026-49852

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.7.4, joserfc.jws.deserialize_json() accepts a JWS General JSON Serialization with an empty signatures array as authenticated. The verify_general_json() loop performs no iterations for the empty array and returns success because no signature check failed, allowing an attacker without a signing key to supply an arbitrary payload that relying applications may treat as authentic. The issue affects the General JSON Serialization path; compact JWS and JWT decoding, Flattened JSON serialization, and JWE JSON processing do not follow this vulnerable path. This issue is fixed in version 1.7.4.

joserfc is a Python library implementing JOSE standards. Prior to 1.7.6, compact JWS deserialization calls bytes.split() before enforcing existing aggregate segment-size limits. When attacker-controlled compact serialization bytes reach deserialize_compact(), the split creates copies of the header, payload, and signature segments before ExceededSizeError rejects them, causing an additional allocation approximately proportional to the supplied token.

In joserfc prior to 1.7.5, joserfc.jwe.decrypt_json() accepts a JWE General JSON Serialization recipients array without a count limit and calls decrypt_cek() for every entry. An unauthenticated attacker can control the number of private-key decryption operations performed by one request.

joserfc, a Python library implementing JOSE standards, prior to version 1.7.3, has a vulnerability in JWTClaimsRegistry that applies membership matching to list-valued iss and sub claims, allowing an array-valued iss containing the expected issuer to pass an intended equality check and enabling issuer-validation bypass.

The Python library joserfc versions 1.7.1 and earlier accept JWTs with trailing padding (==), which is non-conforming to JOSE specifications. This leads to token malleability, potentially allowing bypass of token revocation or anti-replay protection.

The joserfc library in versions 1.3.4 through 1.6.5 accepts oversized JWS payloads without proper length checks, potentially leading to resource exhaustion. This issue has been fixed in version 1.6.7.

In joserfc versions from 1.3.3 to before 1.3.5 and from 1.4.0 to before 1.4.2, ExceededSizeError exception messages embed non-decoded JWT token parts, which may cause Python logging to record an arbitrarily large, forged JWT payload. The issue has been patched in versions 1.3.5 and 1.4.2.